Water vapour condensation on the surface of bulky fruit: Some basics and a simple measurement method

In the postharvest chain of fruit and vegetables, temperature fluctuations frequently occur in the surrounding air, which can lead to condensation of water vapour on the surface of fresh produce. Such processes can have a negative impact on the shelf life of horticultural products. Available sensors for measuring condensation phenomena, in particular on the curved surfaces of bulky fruit, are not suitable or can only be used to a very limited extent. The aim of the present study was to measure condensation on curved surfaces of bulky fruit and to evaluate the influence of the process parameters involved. Some fundamental aspects of condensation on the surface of single apples were analysed using the standard methods of condensation measurement that involve the continuous weighing of the product and measuring the dew-point undershoot. In the context of two typical postharvest scenarios, an in-house developed sensor based on the electrical resistance was tested and validated. The wetness sensor allowed reliable determination of the condensation retention time during re-warming and in both uniform and non-uniform temperature fluctuations on apple fruit. While the retention time of condensed water on the fruit surface was successfully measured, only qualitative statements can be made regarding the intensity of the condensation. •Some basic principles of condensation on the surface of bulky fruits have been studied.•Three independent methods were used to measure condensation processes on individual apples.•An in-house developed sensor to determine the retention time of condensed water was tested and validated successfully. .•We measured condensation on fruit surfaces in two typical post-harvest scenarios.